Synthetic articles of cellulose acetate such as yarn filaments are traditionally produced by melt, wet, or dry spinning techniques, each being very well known in the art. For production of cellulose acetate filaments, the dry spinning technique has been utilized quite successfully in the past. That is, a solution (usually called a "dope" in art parlance) comprising cellulose acetate and a volatile solvent therefore is typically extruded through orifices into a gaseous medium which serves to volatilize and evaporate the solvent, thereby forming filaments of cellulose acetate. Usually multiple filaments are extruded, gathered into a yarn and the yarn is then wound upon a bobbin. Such yarns are then woven into fabrics, for a variety of textile end uses including garments, draperies and the like. Also, the cellulose acetate may be extruded into tow for use in making cigarette filters.
Solvents normally used in the dope are acetone and methylene chloride. Such solvents can easily escape into the environment, necessitating costly preventive measures. Reductions of such solvents is desirous.
Supercritical and near supercritical fluids have previously been described for: recycling cellulose esters from the waste from cigarette manufacture (See U.S. Pat. No. 5,328,934); removal of adhesives from cellulose (See U.S. Pat. No. 5,009,746); terpenes and oils from wood (See U.S. Pat. No. 4,308,200); lignin from Kraft streams (See U.S. Pat. No. 4,493,797); and removal of the natural oils from plant matter (See U.S. Pat. No. 4,675,198). Commercial applications of this technique include: the decaffeination of coffee and tea; extraction of hops flavors for beer manufacture; and denicotination of tobacco. Such commercial processes are well known to those skilled in the art and are described in reviews such as: McHugh and Krukonis, Supercritical Fluid Extraction: Principles and Practice, Butterworths; (1986); Eckert et al., Environmental Science and Technology, Vol. 20, pp. 319-325, (1986); "Supercritical Fluids", Kirk-Othmer Encyclopedia of Chemical Technology 3rd, John Wiley & Son, New York, each of the foregoing are incorporated herein by reference.